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In answer to:
- "Please show the source of $T$ contains $S$. According to Book:Paul R. Halmos/Naive Set Theory, $T$ contains $S$ means $S \in T$ rather than $T \supseteq S$."
1965: Seth Warner: Modern Algebra: "We shall say that a set $E$ is contained in a set $F$ or is a subset of $F$ if every element of $E$ is also an element of $F$." --prime mover (talk) 01:56, 24 July 2018 (EDT)
- Thank you for your reply. However I found out that in 1965: Seth Warner: Modern Algebra, the use of contain sways between $\ni$ and $\supseteq$. So personally I still prefer to use contain for $\ni$ and include for $\supseteq$. Just as Book:Paul R. Halmos/Naive Set Theory writes and Element_(mathematics) explains. --DingChao (talk) 03:15, 24 July 2018 (EDT)